Method and apparatus for flame working spallable material



Jan. 21, 1969 J. L. oussouao METHOD AND APPARATUS FOR FLAME WORKING SPAIJLABLE MATERIAL Filed Sept. 29, 1966 Sheet mmPEmwmEmL.

DISTANCE DIAMETER ENTROPY INVENTOR JULES L. DUSSOURD F76. FIG. M

Jan. 21, 1969 .1. 1.. pussouno METHOD AND APPARATUS FOR FLAME WORKING SPALLABLE MATERIAL Filed Sept. 29, 1966 Sheet 2 INVENTOR JULES L. OUSSOURD United States Patent 7 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for flame working spall able material such as taconite which provides for alternate compression and expansion of the mixture which results from burning fuel and an oxidant. This increases the effective temperature of the burned mixture.

This invention relates to an improved method and apparatus for drilling holes in hard rock such as taconite and other mineral formations which cannot be easily drilled using ordinary percussion type drills.

In prior flame cutting apparatus for drilling holes in such material, fuel and oxidant burn in a combustion chamber and the resulting buring mixture is directed against the surface of the rock. The heat obtained from the combustion of fuel and oxidant such as air or pure oxygen is often insufiicient to properly spall the rock. Even where it is sufficient, the prior apparatus is often ineflicient because a great amount of fuel and oxidant are required to obtain a given temperature.

It is the principal object of this invention to provide a method and apparatus for use in flame working a spiallable mineral body which produces the required amount of heat yet is more efficient.

It is another object of this invention to provide a device of this character which will produce a higher effective temperature from a fuel which has the same combustion temperature.

In general, these objects are carried out by providing a combustion chamber, conduit means for introducing fuel and oxidant into the combustion chamber at a rate and pressure sufficient to affect the burning of the mixture, means adjacent the combustion chamber for directing the resulting burning mixture against a mineral body, and means mounted on the directing means for increasing the effective working temperature of said burning mixture above the combustion temperature of the fuel and oxidant. There is also provided means for cooling the combustion chamber.

The aforementioned and other objects will become apparent from the following description and drawings in which:

FIGS. 1 and 1A are schematic diagrams of the general principle involved in this invention;

FIG. 2 is a graph showing how the temperature and pressure are built up as the apparatus of this invention operates;

FIG. 3 is a graph showing the relationship of nozzle size to the distance from the nozzle to the hole to be drilled;

FIG. 4 is a longitudinal sectional view showing one embodiment of this invention; and

FIG. 5 is a sectional view similar to FIG. 4 showing a second embodiment of this invention.

Referring to FIGS. 1 andlA, a nozzle is generally indicated at 1 and may include a combustion chamber and other standard components. A flame 2 is directed against the surface of a hard rock formation 3 to drill a hole 4. As the flame continues to be directed into the hole, the pressure of the combustion gases in the hole increases. When the pressure at the bottom of the hole reaches a certain point, i.e., a greater pressure than the pressure of the oncoming gas, the gases trapped at the bottom must escape. In order to escape, the gas at the bottom of the hole pushes the oncoming flame aside as shown in FIG. 1A. In the latter position FIG. 1A there are no trapped gases in the hole, and the jet has a tendency to return to the position of FIG. 1. Thus, it can be seen that both FIG. 1 and FIG. 1A are unstable with the result that the flame jet tends to oscillate between the two positions at a high frequency in a resonant mode of several hundred cycles per second. The trapped ga at the bottom of the hole is alternately compressed and decompressed. This pulsing results in the gas temperature being increased to a great extent because of the energy losses associated with the successive compressions and expansions.

As best shown in FIG. 2, there is an increase in temperature and pressure in a continuou pattern. On the temperature-entropy diagram when the flame jet is in position of FIG. 1, the pressure at the bottom of the hole rapidly increases to P When the flame jet is in the position of FIG. 1A, the pressure at the bottom of the hole rapidly drops back to P After a short period of time the temperature at the hole bottom reaches a mean value, midway between points A and B in FIG. 2 while oscillating between a maximum, as indicated at point A in FIG. 2 and a certain minimum indicated at point B. Thi results in an effective working temperature of the average between A and B.

In order to achieve the highest temperatures, the diameter of the nozzle should be approximately one-fourth the distance from the nozzle to the bottom of the hole. As indicated in FIG. 3, the maximum temperatures may be varied by changing this ratio. Thus if a lower increase in temperature is desired, the distance from the nozzle to the hole may be increased.

The temperature of the gas at the bottom of the hole minus the temperature of the gas in the combustion chamber is proportional to the temperature change experienced by the gas during its expansion through the nozzle. Thus:

Where:

T temperature of the combustion gases at the bottom of the hole;

T ternperature of the combustion gases in the combustion chamber;

T =temperature of the combustion gases in the expanded state; and

K=a constant experimentally determined to equal 4 when the ratio of the pressure of the supply to the pressure of the expanded gas is 5.

From the type of rock to be drilled it can be readily determined the temperature required to spall the rock. The temperature of the expanded gas can be measured or calculated for a variety of bottom hole temperatures and supply temperatures. Using the above formula, the required temperature of the gas in the combustion chamber can be calculated. Thus if the temperature in the combustion chamber is 2000 Rankine and the pressure ratio is 5:1, the temperature at the bottom of the hole will be 5000 Rankine. Thus a lower temperature of combustion can be used to achieve a given temperature useable flame.

From the foregoing it can be seen that a greater temperature is produced at the bottom of the hole while using fuel which produces a lower temperature flame, or the same oxidant and fuel can be used at a lower pressure to achieve a greater temperature, thereby making a more economical unit.

Referring now to the apparatus of this invention, FIG. 4 shows a conventional nozzle arrangement genrally indicated at 10. This includes an outer casing 11 secured to a tube 15. A housing 13 including a combustion chamber 12 which is lined with a poured ceramic 14 is mounted within the casing 11. A supply means 16 having a conduit 17 for supplying fuel with a nozzle 19 screwed into the conduit. An oxidant supply conduit 18 passing therethrough is secured to the housing 13. These conduits are used to introduce fuel and oxidant into the combustion chamber 12 at a sufficient rate and pressure to affect burning of the mixture. They may be connected to any suitable supply such as tanks containing fuel and oxidant under pressure.

The lower end of the chamber 12 becomes a means for directing the burning combustible mixture towards the mineral body 40. Means for increasing the temperature of the burning mixture by alternately compressing and decompressing the burning mixture is indicated at 30. This is simply a tubular member secured to the directing means by suitable means such as screws 31 and having open portions 32. The tubular member 30 is preferably made of ceramic but may be made of any other heat resistant material. Since it will not carry any load, strength of this tube is secondary to heat resistance.

When compared with FIG. 1 as the burning combustible mixture passes down into the tubular member 30 towards the bottom of the hole 41, pressure is built up within the tubular member. In order for the gases trapped in the bottom of the hole to escape, they push the flame aside and out the opening 32 in the tube 30, as shown by the dotted arrows, into a position similar to that of FIG. 1A.

FIG. is similar to FIG. 4 except that a different modification of the means for increasing the temperature of the flame is used. In this case a baffle .plate 130 which is solid at its lower end and bifurcated at its upper end Where it is secured to the directing means. Like the tubular member 30 of FIG. 4, the baflie is preferably made of a ceramic. Around the upper portion of this baflie plate, there is a generally bell-shaped housing 132 which is secured to the directing means by screws 131. This bell housing covers a portion of the opening 133 in the baffle plate 130 and directs the burning mixture on opposite sides of plate 130.

As the flame comes out of the combustion chamber 12, it will tend to go on one side or the other of the baflie plate. When the pressure on one side builds up, the flame will be forced over to the opposite side of the plate for the same reasons as explained in connection With FIGS. 1 and 1A and 4 and as indicated by the dotted arrows.

If desired, the nozzle may include a water cooling means which forces Water into the casing 11 to cool the combustion chamber. This cooling water results in steam being formed which passes through the openings 21 and aids in removing spalled material.

The method of this invention should be apparent from the foregoing. Fuel and oxidant are introduced into the combustion chamber at a rate and pressure to affect the burning-of the mixture. The resulting burning mixture is then directed against the mineral body. The temperature of the burning mixture is increased above the combustion temperature of the fuel and oxidant by alternate compression and decompression by using the batfle plate or the tube 30.

From the foregoing it can be seen that the objects of this invention have been carried out and it is intended that the description not be limiting in any way and that the invention be limited only by that which is Within the scope of the appended claims.

I claim:

1. The method of boring a hole by flame working a spallable mineral body comprising the steps of:

introducing into a combustion chamber a combustible mixture of fuel and oxidant at a rate and pressure sufficient to aifect the burning of said mixture;

directing the resulting burning mixture against said mineral body; and

increasing the effective working temperature of said burning combustible mixture by alternately compressing and decompressing said burning mixture within the hole being bored.

2. The method of claim 1 further including the step of removing the spalled material from the working area.

3. The method of claim 2 further including the step of cooling the combustion chamber.

4. Apparatus for boring a hole in a body by flame working such body comprising:

a combustion chamber;

conduit means for introducing into said combustion chamber a combustible mixture of fuel and oxidant at a rate and pressure sufficient to affect burning of the mixture; means adjoining said combustion chamber for directing the resulting burning mixture against said body; and

means mounted on said directing means and cooperating with the hole being bored for increasing the eifective working temperature of said burning mixture above the combustion temperature of said fuel and oxidant.

5. The apparatus of claim 4 wherein said temperature increasing means includes a tubular member having an open side portion.

6. The apparatus of claim 4 wherein said temperature increasing means is a baflie plate having a bifurcated portion adjacent said directing means and a bell-shaped guide mounted on said directing means for directing said burning mixture on opposite sides of said bafiie.

7. The apparatus of claim 4 further including means for cooling said combustion chamber.

References Cited UNITED STATES PATENTS 2,882,017 4/1959 Napiorski -14 3,211,242 10/ 1965 Browning 175-14 3,255,802 6/1966 Browning 175--14 X DAVID H. BROWN, Primary Examiner. 

